Such transceiver arrangements include a transmitter arrangement which itself includes:
n modulation means each of which has an input coupled to a respective one of the input terminals and is able to modulate a respective one of an electrical subcarrier waveforms having an assigned frequency with the information signal applied to the input, and PA1 conversion and combining means having inputs connected to the outputs of said modulation means and an output at which a composite optical signal derived from said modulated subcarrier waveforms is generated, the composite optical signal being transmitted to the receiver arrangement over the optical waveguide. PA1 modulating electrical subcarriers having assigned subcarrier frequencies with said information signals; PA1 converting said modulated subcarriers to optical signals which are transmitted to said receiver arrangement over said optical waveguide.
Such a transceiver arrangement is already known in the art, e.g. from the published German patent application DE-A1-3907495.
In this known transceiver arrangement each of the modulation means has a fixed assigned carrier waveform frequency and therefore a fixed assigned bandwidth capacity which may only be used by the substation connected to the corresponding input terminal. This means that in some cases, when part of the bandwidth capacity is not used, e.g. when supporting narrowband services or when the substation is temporarily not transmitting information signals, the free bandwidth cannot be made available to other substations. In addition, the more substations use the transceiver arrangement, the more difficult it becomes to assign new and usable subcarrier waveform frequencies to the modulation means used by the new substations.
Another consequence of having a relatively high number of substations is that, at the receiver arrangement side because of the number of light signals falling simultaneously on conversion means, more particularly a light detector, included in that receiver arrangement, shot noise and optical interference noise may increase.